The present invention relates to a tape address synchronizing apparatus for a video tape recorder (VTR) which synchronizes a tape position identified by a tape address of a playing VTR with that of a recording VTR or with a reference.
Tape address synchronization affecting the playing VTR is required and the recording VTR when a video program delivered from the playing VTR is edited into a predetermined tape position of the recording VTR. As part of the tape address synchronization, a pre-rolling operation is first carried out during which both devices are rolled to an edit point, and simultaneously tape the addresses of both the VTRs are monitored and tape movement is controlled to cause the addresses to coincide with each other. U.S. Patent Appln. Ser. No. 612,685 "TAPE ADDRESS SYNCHRONIZING APPARATUS FOR VIDEO TAPE RECORDER" filed May 22, 1984 now U.S. Pat. No. 4,587,574 discloses an apparatus of this type. In the referenced application, a tape address is produced by using timing pulses which are delivered from a timer roller mechanism. On the other hand, a VTR currently in use derives time code of from respective frames recorded on a magnetic tape from which tape addresses are produced. According to a prior art approach, in the tape address synchronizing operation for the current VTR, the time code is read out as a tape address, and the tape address is compared with a reference address or another time code of another VTR. The comparison results, are used in conjunction with a feedback control which uses a capstan servo circuit to drive the read out time code i.e. tape addresses to match the reference address.
Simultaneously, the capstan servo circuit is also operated such that the phase of a control track (CTL) signal recorded on the magnetic tape coincides with the phase of an external reference signal. In this case, the reference address is produced in comparison to the external reference signal. The reference to the external signal provides an index at which an actual tape address of the magnetic tape should be located. Thus, in such prior art tape address synchronizing apparatus, a first lock-in range is based on comparisons between the tape address and the reference address, and a second lock-in range is based on comparisons between the CTL signal and the external reference signal. Both ranges are independent of each other, and do not necessarily coincide. Therefore, a synchronization error frequently occurred in the tape address synchronization.